Special rs232 cable for the Tandy Portable Disk Drive aka Brother FB-100 aka KnitKing FDD19

The cable needs to translate between rs-232 and ttl, and needs a special plug shape on one end.

The circuit here, using 3 internally biased transistors, relying on pullup resistors in the Model 100 computer to do part of the job, is the same as in the original cable from Tandy that shipped with the drive.

http://tandy.wiki/TPDD

You also need the 3D printed plug housing and a generic serial cable with a factory molded DB25 male connector on one end. Don't make your own db25 cable end with a typical db25 backshell that you assmble yourself. That type of backshell doesn't fit all the way into the serial port on a Model 100 (or any of the clones). The backshell housing interferes with the computer case and prevents the db25 from inserting all the way. It still makes a connection just not very good. A molded cable inserts all the way.

Wiring and building directions are in the main readme on github.

https://github.com/bkw777/TPDD_Cable

Print the wiring worksheet and fill in the wire color to pin number table by using a multimeter in continuity mode. Use an alligator clip to connect a wire to one meter lead, and probe each pin with the other meter lead to find which pin that wire connects to, then write down the color for that pin number on the work sheet.

The 3d printed soldering jig is just for soldering the 2x4 connector to the pcb because the alignment matters. Not for soldering the transistors or the wires.

Then solder the wires to the pcb by matching the TX color on the worksheet to the TX pad on the PCB, etc.